Understanding the epidemiology of major depressive disorder (MDD) and the neurobiologic theories behind depression and antidepressant treatment is vital for physicians who must identify and treat patients with this disorder. The epidemiology of MDD reveals that this disorder is widespread: the lifetime prevalence of MDD is estimated to be ∼17% and the 12-month prevalence is ≥7%, according to the National Comorbidity Survey Replication. Epidemiologic studies suggest that in any 30-day period, 2% to 5% of the United States population meet criteria for MDD. In addition, nearly twice as many women as men (21% versus 13%, respectively) are affected by a depressive disorder during their lifetimes. These numbers reveal a vast population of people affected by MDD, making depression a tremendous social and medical concern.

Adult attention-deficit/hyperactivity disorder (ADHD) and the spectrum of depressive disorders have high overlapping prevalence rates. Rates of depression in adults with ADHD and rates of ADHD in depressed adults provide an important epidemiologic background for clinicians treating either or both of these populations. There is a distinctive phenomenology of ADHD and depression, and distinctive diagnostic issues that present with the coexistence of these two disorders.

There is a complex overlap between major depressive disorder (MDD) and attention-deficit/hyperactivity disorder (ADHD). The different therapeutic options for adult ADHD mirror those used for children with ADHD. Both stimulant and nonstimulant medications are used to treat the disorder.

As a general principle, separate treatments are often needed for attention-deficit/hyperactivity disorder (ADHD) and comorbid psychiatric disorders. There are few treatments for mood disorders that also treat ADHD, and vice versa. This discussion will review the literature on agents that are effective for both disorders, or that may potentially be combined. Physicians must bear in mind that none of these agents is approved by the Food and Drug Administration for the treatment of comorbid ADHD and depression.